I. Impacts of Poor Flatness on the Mating Surface Between IGBT Package Base and Heat Sink
Degraded Heat Dissipation
Poor flatness of the mating surface reduces the contact area and contact tightness between the IGBT package base and heat sink, hindering heat transfer and deteriorating thermal performance.
Excessive heat generated during IGBT operation cannot be dissipated in a timely manner, leading to a rise in internal temperature. High temperatures accelerate device aging and degrade its reliability and service life.
Increased Thermal Stress
Gaps formed due to uneven mating surfaces induce thermal stress under temperature fluctuations, imposing extra load on the package structure.
Long-term thermal stress may cause cracks, delamination or deformation inside the package, which further compromises the electrical performance and reliability of the device.
II. Short-Circuit Failure Mechanism of IGBTs
Short-circuit failure of IGBTs is generally caused by a combination of multiple factors, including but not limited to the following:
Internal Defects
Process defects and material defects generated during manufacturing may trigger device failure under thermal stress.
External Factors
External conditions such as overvoltage, overcurrent and electrostatic discharge can directly damage the internal structure of IGBTs or degrade their performance.
Poor Heat Dissipation
Prolonged exposure to high temperatures accelerates IGBT aging and weakens its capability to withstand current and voltage, thereby increasing the risk of short-circuit failure.
III. Indirect Correlation Between Poor Flatness and Short-Circuit Failure
While poor flatness of the mating surface between the IGBT package base and heat sink does not directly cause short-circuit failure, it elevates the failure risk indirectly by impairing heat dissipation and inducing extra thermal stress. Details are as follows:
High Temperature Caused by Deteriorated Heat Dissipation
As mentioned above, uneven mating surfaces degrade heat dissipation and keep the IGBT operating at high temperatures. High heat accelerates device aging, reduces reliability and service life, and further increases the probability of short-circuit failure.
Structural Damage Induced by Increased Thermal Stress
Uneven contact surfaces generate additional thermal stress and place extra load on the package. Long-term thermal stress may lead to cracks, delamination or deformation inside the package. Such structural damage can break internal electrical connections or degrade device performance, raising the risk of short-circuit failure.
IV. Countermeasures
The following solutions can mitigate the adverse impacts of uneven mating surfaces on the reliability and service life of IGBTs:
Improve Mating Surface Flatness
Strictly control manufacturing processes and parameters during packaging to ensure the flatness of the contact surface between the IGBT package base and heat sink meets specifications.
Optimize Thermal Design
Adopt high-efficiency heat dissipation structures and materials to improve thermal performance and lower the operating temperature of devices.
Enhance Thermal Management
Conduct regular thermal monitoring and maintenance on IGBT modules to detect and resolve potential heat dissipation issues in a timely manner.
Upgrade Device Quality
Use high-quality raw materials and advanced manufacturing processes to reduce internal defects and failure rates.
In conclusion, there is an evident indirect correlation between poor flatness of the mating surface and IGBT short-circuit failure. Therefore, great importance should be attached to contact surface flatness throughout the manufacturing, operation and maintenance of IGBTs, and effective measures shall be implemented to address related issues.
Actual Measurement Case of IGBT Package Mating Flatness
(The color map presents 3D height distribution; the table shows the measured deformation values.)
V. Introduction to Laser Frequency Comb 3D Optical Profiling System
This 3D optical profiling system operates on the laser frequency comb principle and adopts high-frequency laser pulse time-of-flight ranging technology. It is not affected by occlusion issues prevalent in conventional optical measurement, making it well-suited for various large and complex structural components. It effectively addresses measurement challenges posed by deep holes, grooves and similar features. With a laser repetition rate of 500 kHz, it delivers innovative technology for automated inspection.
Technical feature 1: Coaxial epi-illumination, flight ranging and scanning method, eliminating the traditional optical "obstruction" issue.
Actual case: Valve body oil circuit board with criss-crossing grooves
Technical feature 2: With an accuracy of ±2um, it can achieve scanning and imaging up to a maximum height/depth of 130mm
Technical feature 3: It can be equipped with multiple lens combinations to achieve scanning with a wide field of view spanning tens of meters.
